Bidirectional C and N transfer and a potential role for sulfur in an epiphytic diazotrophic mutualism

• Published in: The ISME Journal Vol. 14; no. 12; pp. 3068 - 3078
• Main Authors: Stuart, Rhona K., Pederson, Eric R. A., Weyman, Philip D., Weber, Peter K., Rassmussen, Ulla, Dupont, Christopher L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2020; Nature Publishing Group
• Subjects: 45/70; 631/158/855; 631/449/2668; 631/45/47; 704/158/2466; Alkanes; BASIC BIOLOGICAL SCIENCES; Biomedical and Life Sciences; Boreal forests; Carbon; Carbon cycle; Cyanobacteria; Ecology; Evolutionary Biology; Image resolution; Life Sciences; Mass spectrometry; Mass spectroscopy; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; Monooxygenase; Mosses; Mutualism; Nitrogen; Nitrogen Fixation; Nostoc; Nostoc - genetics; Nutrition; Regulators; Site-directed mutagenesis; Sulfur; Sulfur compounds; Symbiosis
• ISSN: 1751-7362; 1751-7370; 1751-7370
• DOI: 10.1038/s41396-020-00738-4

In nitrogen-limited boreal forests, associations between feathermoss and diazotrophic cyanobacteria control nitrogen inputs and thus carbon cycling, but little is known about the molecular regulators required for initiation and maintenance of these associations. Specifically, a benefit to the cyanobacteria is not known, challenging whether the association is a nutritional mutualism. Targeted mutagenesis of the cyanobacterial alkane sulfonate monooxygenase results in an inability to colonize feathermosses by the cyanobacterium Nostoc punctiforme , suggesting a role for organic sulfur in communication or nutrition. Isotope probing paired with high-resolution imaging mass spectrometry (NanoSIMS) demonstrated bidirectional elemental transfer between partners, with carbon and sulfur both being transferred to the cyanobacteria, and nitrogen transferred to the moss. These results support the hypothesis that moss and cyanobacteria enter a mutualistic exosymbiosis with substantial bidirectional material exchange of carbon and nitrogen and potential signaling through sulfur compounds.